Generally, the conventional wheeled chairs might be classified into two types, i.e., a three-wheel type and a four-wheel type; such wheeled chairs may also be classified into a non-shock-absorber type and a shock-absorber type. Usually, the chair has steel pipe structure and a transmission system; unfortunately, they have their drawbacks in one way or the other as follows:
(1). Non-shock-absorber type: Such a wheeled chair as shown in FIG. 1 is rather popular in the market. The existing requirements for an electro-motive wheeled chair are that it should be able to drive indoors and outdoors. During the chair being driven indoors at a slow speed, the rider would feel rather comfortable because of the floor surface usually being flat and smooth. In the event of being driven outdoors, the rider might feel uncomfortable as a result of shock or shake caused by a rough road surface and a faster driving speed. Further, such a wheeled chair is rather difficult to repair in case of having trouble.
(2). The shock-absorber type: Such type as shown in FIGS. 2 and 3 is deemed a chair which has a better shock-absorbing structure. It can provide a rider with a comfortable ride upon driving outdoors; however, it has the drawbacks of having a complicated structure and a higher manufacturing cost; as shown in FIG. 2, its reinforced rods "A" would cause a higher cost and a longer assembling time; the joint assembly "D" includes many punched and pressed parts, of which the mold costs are rather high. The swinging arm "C" is too long to provide a strong support. Since the bearing block "B" is a plate type, it has a weaker supporting strength.